The All Blacks look set to be without two of their senior, and most physical, players for what they're hoping will be a bounce-back Bledisloe performance at Eden Park on Saturday night.

Both second five Ma'a Nonu (shoulder) and blindside flanker Jerome Kaino (elbow) have been all but ruled out of the second test in as many weeks against the improving Wallabies after they were injured in last Saturday's 12-12 draw in Sydney.

Assistant coach Ian Foster wasn't willing to provide a definitive view on their prospects when he spoke to the media today at the team hotel in Auckland, but he admitted they were resigned to being without them.

"They had scans yesterday, and we'll know more about that tomorrow, but it's highly unlikely they'll be playing on Saturday."

Neither player was able to train today and Foster admitted the outlook was pretty negative. "The signs are they won't be playing on Saturday," he added.

The loss of two such influential figures is a huge blow for the All Blacks ahead of a test they're putting a big focus on. They can retain the Bledisloe Cup for an 11th straight year with victory at a ground where they haven't lost a test since 1994.

The 31-year-old Kaino, who has played 52 tests, has made an impressive return to the New Zealand game this year and deservedly won back his No 6 jersey, from Liam Messam, with a series of impressive performances for both the Blues and All Blacks.

He provides key physicality around the edges and is an important ball-carrier with an ability to get over the advantage line. He's also one of the All Blacks' best one-on-one tacklers.

But Nonu may be an even bigger loss, given the replacement options.

Chiefs co-skipper Messam looks the obvious understudy for the man he lost his spot to, bringing many of the same attributes and probably a little more versatility around the field.

But the all-round package of skills that Nonu now brings to the No 12 position will not be so easily replaced.

The 32-year-old would have been reunited with his record-breaking midfield partner Conrad Smith this week, but now it looks like Crusader Ryan Crotty, who came off the bench in Sydney, will be paired with the All Blacks' newest dad.

Nonu has always had the power game through the midfield channels, but in recent years he's also become a quality distributor - his flat, wide pass is among the best in the game - and adept tactical kicker.

Crotty is a heady sort, has a good workrate and does not make many mistakes. But he has neither the explosiveness nor power of Nonu. There's also a theory that a tandem of Crotty and Conrad Smith would be a little too similar in playing style.

The other option, standout Highlanders rookie Malakai Fekitoa, would be more of a like-for-like swap for Nonu but that might be too much of a gamble for the All Blacks coaches.

Fekitoa has been a specialist centre all of this breakthrough season and Foster admitted today that he was viewed primarily as a bench cover option at No 12 in the national setup.

"The 12 side for Malakai is more of a longer-term prospect," Foster added. "He's designated to cover 12 on the bench. He's spent more and more time there and is looking a little more comfortable.

"So we've got to weigh that up versus the likes of Ryan coming in and carrying on what he did [in Sydney]."

Foster said it was preferable to have complimentary pieces in midfield, but not absolutely necessary.

"Whoever goes in there has got to have all the skillsets we need for 12. We don't want someone just to hit the ball up hard, they've got to be a thinking player, they've got to be able to pass, and to be able kick and assess situations."

The veteran Smith was back today after his wife gave birth to their baby boy in Wellington on Sunday. "He's a very happy man and is jumping out of his skin," Foster added. "It's been a special time for him, and whilst he hated leaving his team it was the right thing to do."

Foster all but conceded Kaino's replacement was a straight decision between Messam and Steven Luatua who covered the spot on the bench last Saturday.

The third option would be to start Sam Cane at openside and move skipper Richie McCaw across to No 6 where he turned out for the Crusaders at the business end of the Super Rugby season.

"They have played together, mainly in the in latter part of games and that could still happen," said Foster of a potential McCaw-Cane tandem. "But I think we've got some reasonably good specialist No 6 options there."

The 32-test Messam has the experience and harder edge to slot back in without missing a beat, while Luatua's value may be on the bench covering second row and the loose with big Blues lock Patrick Tuipulotu still out with a high ankle sprain.

Foster confirmed tighthead prop Charlie Faumuina was available again after missing the trip to Sydney with strep throat.